Emergency Use of Ciprofloxacin

What to know

In an anthrax emergency, you could be exposed to the bacteria that cause anthrax. Taking the prescription antibiotic ciprofloxacin helps reduce the risk of illness and death if you've been exposed.

Image of hands holding a prescription bottle

About ciprofloxacin

Ciprofloxacin is a prescription antibiotic approved by the Food and Drug Administration (FDA) to prevent anthrax.

Anthrax is a serious disease that you can get if you come in contact with infected animals or animal products. You can also get anthrax if you're exposed to it during a bioterrorism event. You can get sick if you breathe in anthrax spores, eat or drink contaminated products, or if the bacteria that causes anthrax enter the skin through a wound or sore. Anthrax is not contagious, so you can't get it from another person who has anthrax.

Information on this page can also be found on a printable factsheet.

During an emergency

In an anthrax emergency, you may receive ciprofloxacin (sip-roe-FLOX-a-sin) to protect you from potential exposure to anthrax bacteria. Public health authorities will provide guidance on who should get the medication.

Start taking the medicine as soon as possible after the emergency until you get guidance from public health officials or your healthcare provider to stop taking it. This guidance will likely be based on how likely it was that you were exposed to anthrax.

If you were told you were potentially exposed to anthrax, take the medicine two times each day, 12 hours apart. To reduce your chance of getting sick, take the medicine as long as you are directed and do not stop taking it early. Most people will be given a 10-day supply to start, but you may have to take it for up to 60 days. Public health officials will tell you whether you need more and how to get it.

Based on its scientific review, the FDA allows using certain lots of ciprofloxacin even after the expiration date. For more information, go to the FDA website.

Instructions for use

  • Take the medication for as long as it's directed, and don't skip doses. Do not take 2 doses at once if you miss one. Take the next dose when it's scheduled.
  • If you have severe kidney disease, you may need a dose change. Talk to your healthcare provider.
  • Do not split, crush, or chew the pills
  • Do not take ciprofloxacin with milk, yogurt, or juices that have extra calcium added
  • Keep the pills dry. Store pills and liquid between 68-77°F (20-25°C) for up to 14 days.
  • If you have trouble swallowing pills, ask your healthcare provider for a different antibiotic that you can crush.

Adults and children 67 pounds (31kg) or more

  • Take 1 pill (500 mg) in the morning with a full glass of water (with or without food).
  • Twelve (12) hours later, take 1 pill (500 mg) in the evening with a full glass of water (with or without food).

Children under 67 pounds (31kg)

  • Follow instructions provided on the liquid ciprofloxacin label.
  • Shake the liquid very well for about 15 seconds before each use.
  • Take the same amount in the morning and evening (12 hours apart) each day for as long as healthcare providers or officials recommend you should take it.

Hotline information‎

Call the poison control center at 1-800-222-1222 if children or pets take the medicine by accident.

Taking with other medicines

You should not take ciprofloxacin are taking Zanaflex (tizanidine) for muscle spasms. Talk to your doctor if you're on a blood thinner like warfarin, an anti-diabetic medicine like glyburide, seizure medicine like phenytoin, theophylline for asthma, or clozapine for schizophrenia. Taking ciprofloxacin may affect how much of these medicines you need.

Ciprofloxacin might not work as well if you take it when you're on some other medicines. Take ciprofloxacin at least 2 hours before or 6 hours after taking:

  • Multivitamins, supplements, or antacids with aluminum, calcium, iron, or magnesium
  • Carafate (sucralfate)
  • Videx (didanosine)
  • Phosphate binders

Side effects

Although there are potential side effects, the benefits of using ciprofloxacin to prevent disease and death from anthrax exposure outweigh the risks.

Talk to your doctor if you have a history of myasthenia gravis because ciprofloxacin may make muscle weakness or breathing problems worse.

Common side effects

Ciprofloxacin can cause your skin to be more sensitive to the sun. Use sunscreen and cover exposed skin. Keep taking ciprofloxacin even if you have some of the following side effects:

  • Mild nausea
  • Vomiting and/or diarrhea
  • Mild sunburn
  • Vaginal yeast infection

Serious side effects

Serious side effects from ciprofloxacin are rare. They include:

  • Closing of the throat or trouble breathing
  • Swelling of the lips, tongue, or face
  • Severe itching or rash, especially hives and wheals (red, swollen bumps on the skin)
  • Severe stomach cramps with fever or bloody or watery diarrhea
  • Yellowing of the eyes or skin, or dark brown or tea-colored urine (jaundice)
  • Pain, burning, weakness of your arms, hands, legs, or feet
  • Unusual bleeding or bruising
  • Pain, swelling, or inflammations of joints and tendons

You should stop taking ciprofloxacin and talk to your doctor right away if you experience these symptoms.

Alternatives to ciprofloxacin

Public health officials will tell you if other antibiotics (such as doxycycline, levofloxacin, or amoxicillin) are available. Talk to public health officials or healthcare providers if you cannot take ciprofloxacin.

Medical compensation

n the rare event that ciprofloxacin causes serious problems, you may be eligible to receive help with medical costs. A federal program may help cover medical costs for those seriously affected by certain medicines or vaccines. Learn more about the Countermeasures Injury Compensation Program (CICP) at hrsa.gov/cicp or by calling 1-855-266-2427 (toll-free).